FIG. 5 and FIG. 6 show a running state and a storage state of an existent coating facility for conducting electrodeposition coating which comprises, along an overhead conveyor 42 formed in a circulation track 41, a loading device 43 for loading works W conveyed from the preceding step to hangers H each at a predetermined loading position P.sub.1, a pretreatment device 44 for applying pretreatment such as cleaning, degreasing and chemical formation to the surface of the works W loaded by the loading device 43, an electrodeposition coating device 45 for forming an electrodeposition coating film on the surface of the works W completed with the pretreatment by the pretreatment device 44, and a transfer device 48 for down loading the works W from the hangers H after completion of the electrodeposition coating in the electrodeposition coating device 45 and transferring them to carriers T, at a predetermined transferring position P.sub.2, to a floor conveyor 47 running in a drying furnace 46 in this order.
The floor conveyor 47 constitutes a circulation track 47a for conveying the carriers T to which the works W are transferred at a transferring position P.sub.2 into the drying furnace 46, conveying the works W after completion of drying to the succeeding step while loading them as they are on the carriers T and returning the carriers T emptied in the succeeding stage again to the transferring position P.sub.2.
Further, in the circulation track 47a of the floor conveyor 47 that returns from the succeeding step is branched to form a reserved carrier storage track 47b for storing the emptied carriers T by the number of the works W being conveyed by the overhead conveyor 42 but not yet conveyed to the drying furnace 46, and the circulation track 47a from the exit of the drying furnace 46 to the succeeding step is branched to form a carrier storage track 47c for storing all the works W which are being conveyed by the overhead conveyor 42 and the floor conveyor 47 in a state loaded on the carriers T.
Then, the carrier storage track 47c is adapted such that, at the instance the conveyance of the works from the preceding step and the conveyance to the succeeding step are stopped, it completes drying for the works W conveying by the floor conveyor 47 and stores them while loading on the carriers T as they are, applies pretreatment and completes electrodeposition coating of the works W conveying by the overhead conveyor 42, transfers them to the carriers T stored in the reserved carrier storage track 47b, conveys them successively to the drying furnace 46, completes drying and then stores them while loading as they are on the carriers T.
The overhead conveyor 42 is branched to form a looped empty hanger storage track 41a from the circulation track 41 that returns from the transferring position P.sub.2 to the loading position P.sub.1 for storing hangers H which are emptied after transferring the works to the carriers T of the floor conveyor 47, when the conveyance of the works W from the preceding step is stopped, so that the empty hangers H may be prevented from corrosion caused when left in the pretreatment device 44 or the electrodeposition coating device 45, and so that the empty hangers H can be delivered immediately to the loading position P.sub.1 as soon as the conveyance of the works W from the preceding step is started.
With such a constitution, during operation of the conveying lines between each of the steps, the hangers are circulately run by the overhead conveyor 42, pretreatment is applied in the pretreatment device 44 while conveying the works W loaded by the loading device 43, electrodeposition coating is conducted in the electrodeposition coating device 45, the works W are re-transferred subsequently by the transfer device 48 to the carriers T of the floor conveyor 47, and the emptied hangers H are returned again to the loading position P.sub.1 to which succeeding works W are loaded and treated continuously.
Then, the floor conveyor 47 is adapted such that empty carriers T returning from the succeeding step along the circulation track 47a or the reserved carriers T stored in the reserved carrier storage track 47b are conveyed to the transferring position P.sub.2, the works W transferred by the transfer device 48 to the carriers T are conveyed into the drying furnace 46 and conveyed as they are to the succeeding step after the completion of the drying.
Then, when the operations for one day are completed, the conveying lines between each of the steps are stopped and conveyance from the preceding step and conveyance to the succeeding step of the works W are stopped, the works W in the drying furnace 46 are stored being loaded as they are on the carriers T in the carrier storage track 47c, while the works W in the pretreatment device 44 and the electrodeposition coating device 45 are completed with the pretreatment and the electrodeposition coating, transferred by the transfer device 48 to the reserved carriers T on the floor conveyor 47, dried in the drying furnace 46 and then stored while being loaded as they are on the reserved carriers T in the carrier storage track 47c, while the hangers H emptied after transferring the works to the carriers T are stored in the empty hanger storage track 41a.
Then, when the conveyance from the preceding step and conveyance to the succeeding step of the works W are started in the next morning, the empty hangers H stored in the empty hanger storage track 41a are delivered to the circulation track 41 of the overhead conveyor 42 and caused to stand-by at the loading position P.sub.1 and the coating operation is started by successively loading the works W conveyed form the preceding step and at the same time, the works W stored in the carrier storage track 47c are successively conveyed together with the carriers T to the succeeding step, and the empty carriers T returned from the succeeding step are delivered to and stored in the reversed carrier storage track 47b successively till the leading work W conveyed by the overhead conveyor 42 reaches the transferring position P.sub.2.
In accordance with the coating facility described above, even when conveyance from the preceding step and the conveyance to the next step of the works W are stopped, since all the works W that are being conveyed in the overhead conveyor 42 and the floor conveyor 47 can be stored in a state completed with the coating and the drying for the coated film, there is no worry that the works are left during or at the completion of the pretreatment, during or at the completion of the electrodeposition coating and, further, left undried during the drying operation, so that the coating quality can be maintained constant.
However, there are problems in this case for the requirement of additionally providing, in a restricted site of a factory site, a space for storing empty carriers T not used during the running state of applying pretreatment, electrodeposition coating and drying to the works W while conveying them, a space for storing all the works W that are being conveyed by the overhead conveyor 42 and the floor conveyor 47 while loading them on the carriers T at the instance the conveyance from the preceding step and the conveyance to the succeeding step of the works W are stopped, and a space for storing empty hangers.
For instance, assuming that 49 sets of works W are conveyed into the pretreatment device 44 and the electrodeposition coating device 45, while 24 sets of works W are conveyed in the drying furnace 46, and that the storage pitch for the hangers H and the carriers T is about 7 m, the entire length of the empty hanger storage track 41a is: 49.times.7.apprxeq.350 m, the entire length of the reserved carrier storing track is: 49.times.7.apprxeq.350 m and the entire length of the carrier storage track 47c is: (49+24).times.7.apprxeq.520 m, so that the total extension of all the storage tracks 41a, 47b and 47c reaches 1200 to 1300 m.
Further, since it is adapted to store all the works W being conveyed in the overhead conveyor 42 and the floor conveyor 47 while loading them to the carriers T, carriers T are required at least by as much as 49+24=73 as the total for the carriers T for conveying the works W in the drying furnace 46 and reserved carriers T for loading the works by the number of them conveyed in the pretreatment device 44 and the electrodeposition device 45.
As described above, since it requires a great amount of carriers T for storing all the works W and a wide storage space, there is a problem of increasing the installation cost.
Further, upon conveying the works W to the succeeding step, the carriers T bring heat in the drying furnace 46 to the outside and are returned being cooled to a room temperature after handing the works W to the succeeding step and they are heated again when entered into the drying furnace 46, so that a great amount of heat in the furnace is lost to result in a problem that a large amount of heat in the drying furnace 46 is consumed to increase the running cost.
In view of the above, it is a technical subject of the present invention to reduce the storing space and the scale of the facility upon storing an identical number of works, thereby improving the space utilization efficiency and decreasing the installation cost, as well as economize the amount of heat consumed in the drying furnace, thereby decreasing the running cost.